Abstract

Advanced Fault Isolation for Microelectronic Packaging Yield
and Reliability Enhancement
David P. Vallett - PeakSource Analytical, LLC - Fairfax, VT
E-Mail: dvallett@peaksourcevt.com
Abstract
Microelectronics development and manufacturing depend on rapid, accurate, high-confidence root-cause
defect identification. ‘Brute-force’ inspection of large-areas by acoustic or x-ray microscopy is timeconsuming, lacks sufficient resolution, and most importantly cannot definitively pinpoint electrically active
defects, and time-domain reflectometry (TDR) is limited primarily to open circuits and can only estimate
location to within millimeters. Three new techniques - EOTPR (electro-optical teraHertz pulsed
reflectometry), LIT (lock-in thermography), and MCI (magnetic current imaging) – can localize buried,
electrically-active defects in thick densely populated matrices and in some cases determine depth,
especially critical with the emergence of highly integrated 3D package schemes.
EOTPR greatly enhances the estimation of the distance to discontinuities within package conductors.
With faster pulse delivery and lower jitter electronics, open-circuits are localized with a resolution of
microns (vs. millimeters with conventional TDR). Lock-in thermography uses a pulsed power source to
minimize thermal diffusion to localize short circuits to single microns with sensitivity down to microwatts.
The phase between the power and resulting signal is also used to estimate depth. MCI uses a SQUID
(superconducting quantum interference device) to image current from buried conductors and defects by
the magnetic fields generated. Leakages, shorts, and opens are localized with resolution to microns and
sensitivity to femtoWatts.
This presentation briefly discusses operating principles, illustrates examples including 3D, comparatively
summarizes key attributes and limitations, and describes benefits to package manufacturers, buyers, and
integrators.
References:
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Fig. 1: EOTPR (electro-optical TeraHertz pulsed reflectometry) data estimating open circuit
locations in a BGA package to <75 microns separation.
Fig. 2: LIT (lock-in thermography) isolation of a shorted power supply in a plastic encapsulated
wirebond device.
Fig. 3: MCI (magnetic current imaging) isolation of shorted pins in a plastic encapsulated
wirebond device.